As in the initial 3 years of the funded research, an attempt to determine the pathogenesis of meibomian keratoconjunctivitis (MKC) will be made. Patients with all types of chronic blepharitis will be evaluated fully as well as age and sex matched controls. The relative frequency of the various forms of chronic blepharitis will be determined and an attempt will be made to bring up to date the classification of the the blepharitides. All patients will be fully evaluated ophthalmologically and dermatologically. The latter will be done to determine the frequency of associated dermatitis with particular attention to sebaceous glands. Cultures from lids, conjunctivae, and meibomian expressions will be taken for aerobic and anaerobic bacterial isolation, identification, and antibiotic sensitivity determination. Bacteria will be assayed for the production of lipolytic enzymatic activity including lipase, cholesterol esterase, fatty wax esterase, and phospholipase. Biochemical analysis of meibomian secretions will be done to determine if a lipid biochemical abnormality is associated with MKC. Tear lysozyme content, lash infestation by Demodex, tear pH, plus meibomian and conjunctival cytology will be done. Appropriate acute and chronic therapy will be determined for each type of chronic blepharitis and new modes of therapy will be evaluated as additional knowledge about the blepharitides is obtained.